By definition, a kilocalorie (or calorie) is the unit of heat equal to the amount of heat required to raise the temperature of 1 kilogram of water by 1°C at 1 atmosphere pressure. In your body, calories are the energy necessary for the body to function properly.
How to calculate your daily calorie intake
When it comes to losing weight or gaining muscle, there are many factors to consider, one of the most important is how many calories you eat everyday. Later on we will discuss about protein, fat and carbohydrate requirements.
There are many ways to calculate the number of calories you need to eat everyday, but the most common and easier methods are:
- Calculating by bodyweight.
- Harris-Benedict equation.
Calculating by bodyweight: This method is the easiest one and the most practical, all you have to do is multiply your bodyweight in pounds by 15. Let's see an example.
My friend Kevin is 24, he's 5'7 and weighs 170 pounds, using this method:
170(15)= 2550 Calories
He would have to eat 2550 calories to MANTAIN HIS WEIGHT.
Harris-Benedict equation: Using Harris-Benedict is a little more complicated, because this equation takes age, height, weight and physical activity levels into account.
Here´s the equation:
- For men:
BMR= 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.76 x age in years )
- For women:
BMR= 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
The result has to be multiplied by physical activity factors, which are as follows.
Little to no exercise:
Daily Calories Needed = BMR x 1.2
Light exercise (1–3 days per week):
Daily calories needed = BMR x 1.375
Moderate exercise (3–5 days per week):
Daily calories needed = BMR x 1.55
Heavy exercise (6–7 days per week):
Daily calories needed = BMR x 1.725
Very heavy exercise (twice per day, extra heavy workouts):
Daily calories needed = BMR x 1.9
My friend Kevin exercises 2 times a week
BMR= 66 + ( 6.23 x 170 ) + ( 12.7 x 67 ) - ( 6.76 x 24 )= 1748 calories
He does light exercise, so we have to multiply his BMR (1748) by 1.375
1748(1.375)= 2403 calories
If we compare both results we have 2550 calories using the bodyweight method and 2403 calories using Harris-Benedict, so they do not vary that much.
Now that we have the number of calories we have to eat everyday to MANTAIN BODYWEIGHT, we have to adjust them so we start losing or gaining weight. Considering the fact that one pound of bodyfat equals to 3500 calories, if we have a 500 calorie deficit or surplus everyday we could lose or gain 1 pound a week, respectively.
If my friend wanted to lose weight he would have to eat between 1903-2050 calories considering the results of the above methods.
In my clinical practice I consider Harris-Benedict to be more accurate, but calculating calories by bodyweight is much more practical and fast.